QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

Earthquake near Loíza, PR

No earthquake was likely felt in Loíza in the 24 hours to 6:02 pm AST (22:02 UTC). The last one was M 4.1, 78 km (48 mi) SE, at 5:44 am AST on 28 October 2026, estimated intensity II (weak) in town; 5 felt reports to USGS. Every earthquake near Loíza

This page: a magnitude 3.1 earthquake was recorded 4 km (2 mi) north-northwest of Loíza, PR, at 9:32 am AST on 23 July 2020 (13:32 UTC), 87 km deep.

USGS: 3 km NNW of Loíza, Puerto Rico

19 km (12 mi) ENE of San Juan, PR · 11 km (7 mi) ENE of Carolina, PR

9:32 am AST, Jul 23, 2020 · · 87 km deep · released about 1,400 lb of TNT

Every earthquake near Loíza Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Loíza Municipio 6 kmCarolina Municipio 11 kmRío Grande Municipio 14 kmCanóvanas Municipio 15 kmTrujillo Alto Municipio 19 kmSan Juan Municipio 19 kmLuquillo Municipio 22 kmGurabo Municipio 23 kmJuncos Municipio 27 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
9:32 am AST on 23 July 2020 ()
Where
4 km (2 mi) north-northwest of Loíza, PR · earthquakes near Loíza
Magnitude
M 3.1 (md)
Depth
87 km below the surface
Felt
no reports yet
Nearest
Loíza Municipio, 6 km WSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2302 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. In Loíza, 4 km away, the estimate is intensity II (weak). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

Earthquakes near other towns within 30 km: Suárez, Vieques, San Isidro, Santa Barbara, Canovanas, La Dolores.

How big was it?

This earthquake released about 1,400 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 240,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 11,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 7,700× the energy of this one
  4. This earthquake M 3.1 about 1,400 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.5× more

Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.

For this area

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 5.1 3 km W of Aguas Buenas, Puerto Rico · 34 km SW of this epicentre
  2. 5.0 3 km N of Brenas, Puerto Rico · 48 km W of this epicentre

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Epicentre 18.4643, -65.8913. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Loíza Municipio, PR 6 km (4 mi) WSW earthquakes near Loíza Municipio
Carolina Municipio, PR 11 km (7 mi) SW earthquakes near Carolina Municipio
Río Grande Municipio, PR 14 km (9 mi) SE earthquakes near Río Grande Municipio
Canóvanas Municipio, PR 15 km (9 mi) S earthquakes near Canóvanas Municipio
Trujillo Alto Municipio, PR 19 km (12 mi) SW earthquakes near Trujillo Alto Municipio
San Juan Municipio, PR 19 km (12 mi) WSW earthquakes near San Juan Municipio

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

37 earthquakes have been recorded within 50 km since this one.

  1. 3.2 38 km N of San Juan, Puerto Rico
  2. 3.5 1 km ENE of Dorado, Puerto Rico
  3. 3.2 36 km NNE of Luquillo, Puerto Rico
  4. 3.0 5 km ESE of Cataño, Puerto Rico
  5. 2.8 1 km NW of Cidra, Puerto Rico
  6. 2.5 19 km N of San Juan, Puerto Rico
  7. 2.9 2 km NNE of Levittown, Puerto Rico
  8. 2.8 6 km N of Martorell, Puerto Rico
  9. 2.9 Puerto Rico region
  10. 2.0 4 km SSE of G. L. Garcia, Puerto Rico
  11. 2.2 1 km SW of H. Rivera Colon, Puerto Rico
  12. 2.9 23 km N of Loíza, Puerto Rico
  13. 3.4 0 km NE of Mucarabones, Puerto Rico
  14. 3.2 42 km NNE of Vieques, Puerto Rico
  15. 3.0 34 km N of San Juan, Puerto Rico

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.